Role of suprachiasmatic nuclei in circadian and light-entrained behavioral rhythms of lizards

2000 ◽  
Vol 279 (6) ◽  
pp. R2121-R2131 ◽  
Author(s):  
Cristiano Bertolucci ◽  
Valeria Anna Sovrano ◽  
Maria Chiara Magnone ◽  
Augusto Foà
Keyword(s):  
Circadian Rhythms ◽  
Constant Temperature ◽  
Locomotor Behavior ◽  
Functional Similarity ◽  
Daily Rhythm ◽  
Constant Darkness ◽  
Suprachiasmatic Nuclei ◽  
Podarcis Sicula ◽  
Behavioral Rhythms

To establish whether the suprachiasmatic nuclei (SCN) of the Ruin lizard ( Podarcis sicula) play a role in entrainment of circadian rhythms to light, we examined the effects of exposure to 24-h light-dark (LD) cycles on the locomotor behavior of lizards with SCN lesions. Lizards became arrhythmic in response to complete SCN lesion under constant temperature and constant darkness (DD), and they remained arrhythmic after exposure to LD cycles. Remnants of SCN tissue in other lesioned lizards were sufficient to warrant entrainment to LD cycles. Hence, the SCN of Ruin lizards are essential both to maintain locomotor rhythmicity and to mediate entrainment of these rhythms to light. We also asked whether light causes expression of Fos-like immunoreactivity (Fos-LI) in the SCN. Under LD cycles, the SCN express a daily rhythm in Fos-LI. Because Fos-LI is undetectable in DD, the rhythm seen in LD cycles is caused by light. We further showed that unilateral SCN lesions in DD induce dramatic period changes. Altogether, the present data support the existence of a strong functional similarity between the SCN of lizards and the SCN of mammals.

Seasonality and role of SCN in entrainment of lizard circadian rhythms to daily melatonin injections

1998 ◽  
Vol 274 (4) ◽  
pp. R1004-R1014 ◽  
Author(s):  
Cristiano Bertolucci ◽  
Augusto Foà
Keyword(s):  
Circadian Rhythms ◽  
Locomotor Behavior ◽  
Suprachiasmatic Nuclei ◽  
Primary Target ◽  
Podarcis Sicula ◽  
Injection Period ◽  
Target Sites ◽  
Locomotor Rhythms ◽  
First Time

To establish whether the capability of daily melatonin injections to entrain circadian rhythms varies with season, we examined in constant conditions the locomotor behavior of lizards Podarcis sicula collected and subjected to daily melatonin injections at different times of the year. Although in summer locomotor rhythms of both pineal-intact and pinealectomized lizards became entrained to the 24-h injection period, in the other seasons their rhythms did not entrain to the injection period. To establish whether the suprachiasmatic nuclei (SCN) mediate summer entrainment of locomotor rhythms to melatonin, we examined the behavioral effects of daily melatonin injections in lizards subjected to either bilateral (SCN-X) or unilateral (USCN-X) ablation of the SCN. SCN-X lizards became behaviorally arrhythmic, and daily melatonin injections did not restore rhythmicity. USCN-X lizards remained rhythmic, and their locomotor rhythms did entrain to the injections. Besides demonstrating for the first time in a vertebrate that daily melatonin injections are capable of entraining circadian rhythmicity in only one season (summer), the present results support the view that the SCN (and not the pineal gland) are the primary target sites of melatonin in the circadian system of P. sicula.

Maternal-fetal communication of circadian phase in a precocious rodent, the spiny mouse

1987 ◽  
Vol 253 (4) ◽  
pp. E401-E409
Author(s):  
D. R. Weaver ◽  
S. M. Reppert
Keyword(s):  
Circadian Rhythms ◽  
Postnatal Period ◽  
Spiny Mouse ◽  
Constant Darkness ◽  
Suprachiasmatic Nuclei ◽  
Maternal Influences ◽  
Circadian Phase ◽  
Environmental Light ◽  
Running Activity ◽  
Free Running

The development of circadian rhythms was examined in a precocious rodent species, the spiny mouse. Spiny mouse pups born and reared in constant darkness expressed robust circadian rhythms in locomotor activity as early as day 5 of life. Free-running activity rhythms of pups born and reared in constant darkness were coordinated with the dam on the day of birth. Postnatal maternal influences on pup rhythmicity are minimal in this species, as pups fostered on the day of birth to dams whose circadian phases were opposite to the pups' original dams were coordinated with their original dams on the day of birth. Studies using 2-deoxy-D-[1-14C]-glucose autoradiography showed that there were synchronous (coordinated) rhythms in metabolic activity in the maternal and fetal suprachiasmatic nuclei, directly demonstrating prenatal coordination of maternal and fetal rhythmicity. Maternal-fetal coordination of circadian phase was not the result of direct entrainment of the fetuses to the environmental light-dark cycle. These results demonstrate that there is prenatal communication of circadian phase in this precocious species, without demonstrable postnatal maternal influences on pup circadian rhythmicity. Spiny mice therefore represent an important animal model in which circadian rhythms in the postnatal period can be used to precisely assess prenatal influences on circadian phase.

scholarly journals Period gene expression in the diurnal degu (Octodon degus) differs from the nocturnal laboratory rat (Rattus norvegicus)

2009 ◽  
Vol 296 (2) ◽  
pp. R353-R361 ◽  
Author(s):  
Andrew M. Vosko ◽  
Megan H. Hagenauer ◽  
Daniel L. Hummer ◽  
Theresa M. Lee
Keyword(s):  
Circadian Rhythms ◽  
Rattus Norvegicus ◽  
Hybridization Signal ◽  
Constant Darkness ◽  
Suprachiasmatic Nuclei ◽  
Octodon Degus ◽  
Period Gene ◽  
Laboratory Rat ◽  
The Relationship

Recent data suggest that both nocturnal and diurnal mammals generate circadian rhythms using similarly phased feedback loops involving Period genes in the suprachiasmatic nuclei (SCN) of the hypothalamus. These molecular oscillations also exist in the brain outside of the SCN, but the relationship between SCN and extra-SCN oscillations is unclear. We hypothesized that a comparison of “diurnal” and “nocturnal” central nervous system Per rhythms would uncover differences in the underlying circadian mechanisms between these two chronotypes. Therefore, this study compared the 24-h oscillatory patterns of Per1 and Per2 mRNA in the SCN and putative striatum and cortex of Octodon degus (degu), a diurnal hystricognath rodent, with those of the nocturnal laboratory rat, Rattus norvegicus. The brains of adult male degus and rats were collected at 2-h intervals across 24 h in entrained light-dark and constant darkness conditions, and sections were analyzed via in situ hybridization. In the SCN, degu Per1 and Per2 hybridization signal exhibited 24-h oscillatory patterns similar in phasing to those seen in other rodents, with peaks occurring during the light period and troughs during the dark period. However, Per1 remained elevated for five fewer hours in the degu than in the rat, and Per2 remained elevated for two fewer hours in the degu. In brain areas outside of the SCN, the phase of Per2 hybridization signal rhythms in the degu were 180° out of phase with those found in the rat, and Per1 hybridization signal lacked significant rhythmicity. These results suggest that, while certain basic components of the transcriptional-translational feedback loop generating circadian rhythms are similar in diurnal and nocturnal mammals, there are variations that may reflect adaptations to circadian niche.

scholarly journals mir-276a strengthens Drosophila circadian rhythms by regulating timeless expression

2016 ◽  
Vol 113 (21) ◽  
pp. E2965-E2972 ◽  
Author(s):  
Xiao Chen ◽  
Michael Rosbash
Keyword(s):  
Circadian Rhythms ◽  
Molecular Clock ◽  
Posttranscriptional Regulation ◽  
Clock Gene ◽  
Constant Darkness ◽  
Transcription Activator ◽  
Behavioral Rhythms ◽  
Culture Cells ◽  
Tissue Culture Cells ◽  
The Central Nervous System

Circadian rhythms in metazoan eukaryotes are controlled by an endogenous molecular clock. It functions in many locations, including subsets of brain neurons (clock neurons) within the central nervous system. Although the molecular clock relies on transcription/translation feedback loops, posttranscriptional regulation also plays an important role. Here, we show that the abundant Drosophila melanogaster microRNA mir-276a regulates molecular and behavioral rhythms by inhibiting expression of the important clock gene timeless (tim). Misregulation of mir-276a in clock neurons alters tim expression and increases arrhythmicity under standard constant darkness (DD) conditions. mir-276a expression itself appears to be light-regulated because its levels oscillate under 24-h light–dark (LD) cycles but not in DD. mir-276a is regulated by the transcription activator Chorion factor 2 in flies and in tissue-culture cells. Evidence from flies mutated using the clustered, regularly interspaced, short palindromic repeats (CRISPR) tool shows that mir-276a inhibits tim expression: Deleting the mir-276a–binding site in the tim 3′ UTR causes elevated levels of TIM and ∼50% arrhythmicity. We suggest that this pathway contributes to the more robust rhythms observed under light/dark LD conditions than under DD conditions.

Comparison of cortisol and rectal temperature circadian rhythms in horses: the role of light/dark cycle and constant darkness

2012 ◽  
Vol 43 (6) ◽  
pp. 681-687 ◽  
Author(s):  
Claudia Giannetto ◽  
Francesco Fazio ◽  
Irene Vazzana ◽  
Michele Panzera ◽  
Giuseppe Piccione
Keyword(s):  
Circadian Rhythms ◽  
Rectal Temperature ◽  
Constant Darkness ◽  
Dark Cycle ◽  
Role Of Light

scholarly journals Long-term in vivo recording of circadian rhythms in brains of freely moving mice

2018 ◽  
Vol 115 (16) ◽  
pp. 4276-4281 ◽  
Author(s):  
Long Mei ◽  
Yanyan Fan ◽  
Xiaohua Lv ◽  
David K. Welsh ◽  
Cheng Zhan ◽  
...  
Keyword(s):  
Circadian Rhythms ◽  
Clock Gene ◽  
Constant Darkness ◽  
Behavioral Rhythms ◽  
Clock Gene Expression ◽  
Hippocampal Ca1 ◽  
Freely Moving ◽  
Term Monitoring

Endogenous circadian clocks control 24-h physiological and behavioral rhythms in mammals. Here, we report a real-time in vivo fluorescence recording system that enables long-term monitoring of circadian rhythms in the brains of freely moving mice. With a designed reporter of circadian clock gene expression, we tracked robust Cry1 transcription reporter rhythms in the suprachiasmatic nucleus (SCN) of WT, Cry1−/−, and Cry2−/− mice in LD (12 h light, 12 h dark) and DD (constant darkness) conditions and verified that signals remained stable for over 6 mo. Further, we recorded Cry1 transcriptional rhythms in the subparaventricular zone (SPZ) and hippocampal CA1/2 regions of WT mice housed under LD and DD conditions. By using a Cre-loxP system, we recorded Per2 and Cry1 transcription rhythms specifically in vasoactive intestinal peptide (VIP) neurons of the SCN. Finally, we demonstrated the dynamics of Per2 and Cry1 transcriptional rhythms in SCN VIP neurons following an 8-h phase advance in the light/dark cycle.

Circadian rhythms of dopamine in mouse retina: The role of melatonin

2002 ◽  
Vol 19 (5) ◽  
pp. 593-601 ◽  
Author(s):  
SUSAN E. DOYLE ◽  
MICHAEL S. GRACE ◽  
WILSON McIVOR ◽  
MICHAEL MENAKER
Keyword(s):  
Circadian Rhythm ◽  
Circadian Rhythms ◽  
High Performance ◽  
Mouse Retina ◽  
Constant Darkness ◽  
Dark Cycle ◽  
Melatonin Synthesis ◽  
Dopamine Content ◽  
C3h Mice

Both dopamine and melatonin are important for the regulation of retinal rhythmicity, and substantial evidence suggests that these two substances are mutually inhibitory factors that act as chemical analogs of day and night. A circadian oscillator in the mammalian retina regulates melatonin synthesis. Here we show a circadian rhythm of retinal dopamine content in the mouse retina, and examine the role of melatonin in its control. Using high-performance liquid chromatography (HPLC), we measured levels of dopamine and its two major metabolites, 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA), in retinas of C3H+/+ mice (which make melatonin) and C57BL/6J mice that are genetically incapable of melatonin synthesis. In a light/dark cycle both strains of mice exhibited daily rhythms of retinal dopamine, DOPAC, and HVA content. However, after 10 days in constant darkness (DD), a circadian rhythm in dopamine levels was present in C3H, but not in C57 mice. C57 mice given ten daily injections of melatonin in DD exhibited a robust circadian rhythm of retinal dopamine content whereas no such rhythm was present in saline-injected controls. Our results demonstrate that (1) a circadian clock generates rhythms of dopamine content in the C3H mouse retina, (2) mice lacking melatonin also lack circadian rhythms of dopamine content, and (3) dopamine rhythms can be generated in these mice by cyclic administration of exogenous melatonin. Our results also indicate that circadian rhythms of retinal dopamine depend upon the rhythmic presence of melatonin, but that cyclic light can drive dopamine rhythms in the absence of melatonin.

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